1. Technical Field
The present invention generally relates to methods and systems for authentication in secure data communications. More particularly, the present invention relates to methods and systems for bi-directionally authenticating the client and the server using a plurality of factors including a public key infrastructure (PKI) certificate.
2. Related Art
Banking, financial services, government, education, and all varieties of companies rely upon advanced computer systems and data communication networks such as the Internet. While such advancements have greatly increased the speed and convenience with which business is conducted, numerous vulnerabilities compromise the security of the highly sensitive and confidential data being exchanged. At the most basic level, electronic transactions typically involve a server computer system and a client computer system communicating over a network. Additional client or server computer systems may also be connected to the network, such that multiple clients may access a given server, or multiple servers may be accessed by a given client. In this open network environment, the primary concern of data security is three-fold. First, the server must be assured that the client is what it asserts it is. Second, the client must be assured that the server is what it asserts it is. Third, any information being exchanged between a legitimate server and a legitimate client must not be intercepted or changed by any other computer systems on the network.
In the electronic banking setting, for example, the bank must authenticate the identity of the user accessing the banking server, so that transactions relating only to a particular customer are permitted, and that the user accessing the banking server is verified as the customer or someone given authority by the customer. The client must be ensured that the banking server is, indeed, the server operated by the bank, and not a similar one operated by a malicious entity. This is known as a phishing attack, where a fake server is made to resemble the legitimate server, and tricks the user into providing confidential information such as bank account numbers, social security numbers, passwords, and the like. Much harm may be inflicted on the customer by a criminal possessing such information, including erroneous accumulation of debt, arrest records, criminal convictions, destruction of creditworthiness, damage to reputation, and so forth. These are also known as identity theft crimes. As confidential information is being transmitted over an open network, such information must be encrypted or otherwise rendered incomprehensible to any other system besides the client and the server. The open nature of the network renders computer systems susceptible to replay attacks, where a valid data transmission is intercepted and repeated later for fraudulent or malicious purposes. For example, passwords or other authentication information may be intercepted, and used later to gain access to sensitive information. Further, the information being transmitted on the network must not be modifiable, such as in the case of man-in-the-middle attacks. This involves an attacker reading, inserting and modifying data between a legitimate client and server with neither recognizing the compromised nature of the link.
A variety of techniques is used to authenticate, or verify the identity of the client. Authentication may utilize one or more factors, which include something a user knows, something a user has, and something a user is. Most often, only a single factor is utilized because of the added cost and complexity of additional authentication factors. In such single-factor authentication systems, the most common is the use of a password or a personal identification number (PIN) to limit access. Another example is an ATM card with a corresponding PIN. The server maintains a list of usernames and corresponding passwords/PINs, and when the entered username and password/PIN combination is determined to be correct after a comparison to the list, access to the system is permitted. The secret nature of passwords and PINs, at least in theory, prevents unauthorized users from accessing the computer system. This technique is ineffective because the authorized users oftentimes mistakenly and unwittingly reveal their passwords or PINs to an unauthorized user. Furthermore, brute-force techniques involving the entry of every combination of letters, numbers, and symbols, as well as dictionary-based techniques, may further compromise the effectiveness of such authentication systems. Because passwords must be memorized, users often choose words that are easier to remember, making it more susceptible to defeat by means of dictionary attacks. On the other hand, the more complex the passwords are required to be, the more likely that the password will be written on something easily accessible, for both the legitimate and malicious user, in the vicinity of the computer. As asserted by the Federal Financial Institutions Examination Council (FFIEC), single factor authentication is a substantial weakness, particularly in financial or banking-related on-line services.
In addition to passwords, an additional factor may be utilized that involves something a user has. These include simple devices that are connected to the client computer through an external peripheral port, as well as sophisticated tokens that generate unique codes or one-time passwords (OTP) that are that are entered in conjunction with a username and a password as described above. Currently available token-based authentication systems include the RSA SecureID, which utilizes a time-synchronized OTP, and the Verisign Unified Authentication, which utilizes a mathematical algorithm-based OTP. While greatly increasing security, token devices are expensive to license, expensive to maintain, and cumbersome for the user to carry. As with any diminutive device, tokens are easy to lose. When lost, it may take days or weeks for a replacement, resulting in additional cost and lost productivity.
A third authentication factor utilizes unique biometric attributes of a person, such as fingerprints, retinal and facial patterns, voice characteristics, and handwriting patterns. Biometric authentication, however, requires the deployment of specialized hardware for acquiring such data including fingerprint and retina scanners, microphones, and the like. Furthermore, specialized databases and software are required for comparing the acquired data to existing user data, otherwise referred to as enrollment data. Thus, the cost of such deployment is prohibitive, and is for the most part limited to large organizations. Additionally, biometric readings may be inconsistent from one acquisition to the next, thereby resulting in false negatives. Though fingerprint identification is being increasingly used in portable computers to secure access to applications and data therein, the use of such devices to authenticate with other computer systems is uncommon because of the need to maintain an enrollment database.
To authenticate the server computer system, and to ensure that data transmissions are not intercepted, the Transport Layer Security (TLS) protocol is frequently utilized. TLS is a cryptographic protocol that provides data exchanges safe from eavesdropping, tampering, and forgery, and is often used for securing web browsing, e-mail, file transfers, and other such electronic transactions. More particularly, TLS operates on the protocol layers below application-layer protocols such as the HyperText Transfer Protocol (HTTP), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), but above the transport level protocols such as the Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP). Various components of a public key infrastructure (PKI) conforming to the International Telecommunications Union-Telecommunications Standardization Sector (ITU-T) PKI standard X.509 are utilized in the TLS protocol.
Generally, public key encryption involves a unique public/private key pair held by both the recipient and the sender. The private key of the sender is retained solely by the sender, and the private key of the recipient is retained solely by the recipient. The public key of the sender is distributed and is held by the recipient, and the public key of the recipient is also distributed and held by the sender. When transmitting a message, the sender's private key and the recipient's public key is used to encrypt the message. The message is decrypted by the recipient using the recipient's private key and the sender's public key. The recipient need not have a unique public/private key pair, however, and instead may utilize a one-time cipher.
TLS is commonly implemented only on a server-side basis, however, and only the server is authenticated. For example, when establishing a secure HyperText Transfer Protocol (HTTP) connection from a client browser to a web server, the client browser retrieves a digital certificate associated with the web server. The certificate, which contains the public key, is used by the browser to authenticate the identity of the web server, and to encrypt a session key transmitted back to the web server for use in encrypting subsequent data. In order to ensure the legitimacy of the server certificate, it is signed by a Certification Authority (CA).
Though the implementation of client-side TLS establishes a bilateral trust between the server and the client and prevents identity theft and phishing attacks, there are a number of significant deficiencies. More particularly, it is necessary for the client to obtain or purchase a certificate properly signed by the CA. Thus, complications associated with certificate ownership are placed on the user. Additionally, implementing client authentication on the server is a cumbersome process, in that additional servers and maintenance is necessary. In addition to the other core functionality provided by the server, it must be configured to issue user certificates.
Accordingly, there is a need in the art for a method and system for authenticating the client and the server without the use of hardware devices such as tokens or the deployment of client-side TLS. There is also a need for such authentication to be over multiple factors. Furthermore, there is a need for an improved method and system for initiating an encrypted data communications session using authentication credentials. There is also a need in the art for an authentication system that is easy to configure and readily integrates with existing servers and clients.